Abstract

Comprehensive post mortem microbial culturing of liver, lung, spleen and peripheral lymph node tissues was performed during 1992 and 1993 at The Marine Mammal Center (TMMC), Sausalito, California. Pinniped species for which data were collected include: Zalophus californianus, Phoca vitulina, Mirounga angustirostris, Callorhinus ursinus and Arctocephalus townsendi. In addition, all 1992 fur seals, harbor seal pups and northern elephant seal pups were screened for rectal flora on admission, at 30 days and at 60 days post admission. Eighty-four isolates of Salmonella were obtained from 865 pinnipeds examined post mortem. Forty two post mortem isolates were serotyped at the National Veterinary Diagnostic Laboratory or at the University of California, Davis. Results included: 21 S enteriditis, 9 S Newport, 9 S. heidelberg, 6 S. St. Paul, 2 S. Montevideo, 1 S. hadar, and 1 S. bardo. Salmonella was determined to be the primary cause of death in 63 cases, 46 of these by bacteremia. Salmonella was isolated from 8 abscesses which were concluded to be the site of entry for later septic processes.

Salmonella St. Paul was the most frequent serotype (10 isolates) obtained from rectal cultures. Rectal culture isolates also included: 11 Salmonella serotype unknown, 3 S. Montevideo, 2 S. Newport. 1 S. hadar, and 1 S. muenster. Eight elephant seals and one harbor seal that had had Salmonella isolated from ante mortem rectal swabs subsequently died of other causes. Only in one harbor seal that had Salmonella on admit rectal swab was death determined to be as a result of Salmonellosis. Rectal Salmonella appeared to be transient and only one positive pup at admit was still positive at 30 days.

Salmonella was a significant pathogen in the species of pinnipeds examined in this survey. These findings underscore the need for further evaluation of the epidemiology of Salmonellosis among free ranging marine mammals.